Speech is an inherently dynamic signal and spectral dynamics are integral to perception of both consonants and vowels. The rate, direction, and extent of formant movements provide cues to consonant and vowel identity. The loss of peripheral auditory sensitivity, precise temporal processing, and frequency selectivity associated with hearing loss and aging will disrupt the perception of formant movements. As a result, the reduction or elimination of dynamic spectral cues may impair speech understanding, especially in adverse listening conditions such as background noise or reverberation. The purpose of this program of research is to understand the perception of dynamic acoustic signals by hearing-impaired listeners, with the long-term goal of improving speech understanding by these individuals, especially in adverse listening conditions. The proposed research compares the performance of normally-hearing and hearing-impaired listeners on a number of tasks designed to assess basic perceptual abilities in response to complex, non-speech auditory stimuli that change in frequency over time. Experimental procedures will consist of adaptive tests of spectral change detection and discrimination in non-speech stimuli which possess timing and frequency characteristics to those of speech, and estimation of spectral change detection and discrimination thresholds in several types of competing background noise and with simulated reverberation. Speech recognition ability in background noise and reverberation will also be assessed. Based on the results of these behavioral measures of spectral change perception and speech recognition, a computational model will be developed that can account for differences in speech intelligibility due to hearing status and stimulus characteristics. The effectiveness of the computational model will be evaluated by comparing model predictions with actual listener performance. The application of information regarding spectral change perception to a model of speech recognition will have implications for the development of new hearing aid processing strategies and rehabilitative auditory training programs that may enhance speech intelligibility and reduce listening effort in hearing-impaired individuals.